The "sulfate process" has long been used to extract titanium dioxide from titanium slag. Titanium dioxide is an extremely important chemical product used in a wide variety of ways in various industries. A titanium slag usable in this process typically consists mostly of titanium dioxide, the rest being impurities, primarily the oxides of iron, magnesium, aluminum, silicon, calcium and manganese. The term titanium slag is known in the art to include titanium in slag form, titanium ore and blends of slag and titanium ore.
Briefly, the sulfate process of importance to understand this invention is as follows. Titanium slag is reacted with concentrated sulfuric acid to form titanyl sulfate as well as other sulfates. Next, in a clarification step, the product of the preceding step is separated from the muddy residues that it contains leaving a solution containing titanium sulfate.
The muddy residues obtained at the clarification step are generally filtered, washed, and then transported to a burial site.
The commercial exploitation of the sulfate process produces enormous quantities of waste sulfuric acid. Most industrial installations discharge this acid into oceans and rivers.